The present invention relates to a cutting tool insert comprising of a body of a hard alloy of cemented carbide, cermet, ceramics, cubic boron nitride based material or high speed steel and a coating designed to be used in metal cutting applications generating high temperatures, particularly machining of super alloys and stainless steel. Said coating is composed of at least one layer of a thermally stabilized homogeneous cubic (Ti, Si, Me)N phase, where Me is one or more of the metal elements Y, Hf, Nb, Ta, Mo, W, Mn, Fe and Zn. The coating is grown by physical vapour deposition (PVD) and preferably by cathodic arc evaporation.
TiN has been widely used as hard layer on cutting tools due to its poor oxidation resistance at elevated temperatures, however, the focus has shifted towards more complex ternary and quaternary compounds, e.g. Ti—Al—N, Ti—Al—Si—N and Ti—Cr—Al—N with improved high temperature performance. For example, Ti—Al—Si—N has been reported as super hard, H>40 GPa due to a two phase structure consisting of crystalline phase of NaCl-type in combination with x-ray amorphous Si3N4 or SiNx.
EP 1174528 discloses a multilayer-coated cutting tool insert. The first hard coating film is formed on the insert and a second hard coating film formed on the first hard coating film. The first hard coating film comprises one or more of Ti, Al and Cr, and one or more of N, B, C and O. The second hard coating film comprises Si and one or more metallic elements selected from the group consisting of metallic elements of Groups 4, 5 and 6 of the Periodic Table and Al, and one or more non-metallic elements selected from the group consisting of N, B, C and O.
EP 1736565 discloses a cutting tool insert, solid end mill, or drill, comprising a body and a coating. The coating is composed of one or more layers of refractory compounds of which at least one layer comprises a cubic (Me,Si)X phase, where Me is one or more of the elements Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and Al, and X is one or more of the elements N, C, O or B.
WO 2006/118513 discloses a cutting tool insert, solid end mill or drill, comprising a body and a coating. The coating is composed of a cubic C-(Me, Si,) N-phase without coexisting amorphous phase.
EP 1722009 discloses a cutting tool insert, solid end mill, or drill, comprising a body and a coating. The coating is composed of one or more layers of refractory compounds of which at least one layer comprises a h-Me1Me2X phase, where Me 1 is one or more of the elements V, Cr, Nb, and Ta and Me2 is one or more of the elements Ti, Zr, Hf, Al, and Si and X is one or more of the elements N, C, O or B.
EP 0588350 discloses a hard layer of Ti—Si—N composite material on a body is carried out by using a source of evaporation possessing a composition of TiaSib with a in the range of 75-85 at % and b 15-25 at %.
U.S. Pat. No. 6,033,768 discloses a hard coating consisting of a layer of a binary, ternary or quaternary TiAl based multicomponent material comprising nitride or carbonitride with an Al-content of 10 to 70 at %. The layer contains about 0.1 to 4 at % yttrium unevenly distributed over the entire layer.
JP 2004-338058 discloses a hard coating comprising a compound nitride layer of Ti, Si and Y. The layer has a concentration distribution structure wherein a maximum Si content and a minimum Si content exist in alternate repetition with a spacing of 0.01-0.1 μm. JP 2004-338008 and JP 2004-322279 disclose similar hard coatings comprising a compound (Ti, Si, Cr)N layer and (Ti, Si, Zr)N, respectively.
The trends towards dry-work processes for environmental protection, i.e., metal cutting operation without using cutting fluids (lubricants) and accelerated machining speed with improved process put even higher demands on the characteristics of the tool materials due to an increased tool cutting-edge temperature. In particular, coating stability at high temperatures, e.g., oxidation- and wear-resistance have become even more crucial.
It is an object of the present invention to provide a thermally stabilized (Ti,Si)N coated cutting tool yielding improved performance in metal cutting applications at elevated temperatures.
Surprisingly, it has been found that by introducing small amounts of the metal elements Y, Hf, Nb, Ta, Mo, W, Mn, Fe and Zn in (Ti,Si)N layers leads to improved high temperature metal cutting properties.